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state, but none occurred on the Platte River (Appendices A and 6). [Two radio- <br />tagged yearlings migrating together were observed to make a 22 -day stopover 8 <br />miles west of North Platte, Nebraska in 1984 (FW S 1984b).] During three <br />tracking efforts (one in the spring involving three birds.. and two in the fall <br />involving a total of five birds), no stopovers occurred in the state. <br />2.7.3 Habitat Selection Strategy <br />The manner in which habitat is used by an endangered or threatened species has <br />important bearing on whether or not loss or modification of that habitat will <br />have a detrimental effect on the species' ability to survive and recover. <br />Whooping cranes in the Wood Buffalo-Aransas flock are known to use the same <br />nesting and wintering areas each year through tradition. That is, through <br />tradition the species has developed a dependency on habitat at Wood Buffalo <br />National Park and Aransas NWR for specific life functions. Consequently, these <br />areas clearly constitute "critical habitat" in accordance with the definition <br />provided in the Endangered Species Act (see Section 1.1.1). Similarly, <br />determi nati on of the habi tat sel ecti on strategy appl ied by migrati ng w hoopi ng <br />cranes is essential to assessing the criticality of specific stopover sites <br />along the fl yway. If a given stopover site is used on a traditional basis <br />(i. e. , year after year, usually for extended periods), its loss could adversely <br />affect the ability of migrant birds to secure necessary food and rest. <br />However, if a stopover site is used on a nontraditional basis (i. e. , <br />infrequently, or opportunistically, usually for brief periods when appropriate <br />stimuli influence the birds to look for a place to stop), its loss would likely <br />have no effect on the survival or recovery of the species, assuming that other <br />suitable stopover sites are readily available. <br />By deductive reasoning, Johnson and Temple (1980, <br />whooping cranes, in fact, select stopover habitat <br />nontraditional basis. This conclusion was based <br />ev i de n ce : <br />1) "Although several locations <br />none of them are used every <br />sightings consistently from <br />traditional use by at least <br />these sites can be expl ai ne <br />other than 'tradition'." <br />pp. 63 -66) concluded that <br />along the flyway on a <br />on the following lines of <br />have had many sightings over the years, <br />year by every bird, and in fact, none have <br />year to year, which might indicate <br />a pair of bi rds... CM]ore frequent use of <br />d satisfactorily by a combination of factors <br />2) "Whooping cranes use a wide variety of types and 'qualities' of <br />habitats for roosting and feeding, which when considered together, <br />indicate that the birds are quite fl exi bl e in their ecological <br />requirements during migration. Therefore, historically, there was no <br />selective advantage for whoopers to develop a habit of traditional use <br />of certain high ' qual ity' sites because other suitable sites were <br />widely available." <br />3) " Whoopers have used roosts of apparently lower ?quality' in areas where <br />higher 'quality' sites were readily available. This indicates...that <br />whooping cranes are not under a strong stimulus to find sites offering <br />2 -19 <br />